This invention relates to a pattern forming apparatus and, more particularly, to an image forming apparatus, which can selectively print document image information and type face patterns, e.g., characters, numerals, and symbols.
Recently, electrographic apparatuses employing wire dot printers, thermal dot printers and laser dot printers have come into general use. Such electrophotographic apparatuses use an optical scanner for scanning a document to produce image information relating thereto. The image information so produced is converted into digital image signals, and a dot printer is driven according to the digital image signals to print the document pattern as a dot print configuration. In such a dot printer, the higher the dot density, the more faithfully the document pattern can be reproduced. The dot printer can also print character patterns generated from a character generator. In an electrographic apparatus which can print out both document image information from the scanner and character patterns from the character generator, as described above, the dot pattern is commonly used to print out the document image information and character patterns. In this case, the dot density of the dot pattern is set at high value so that image information can be faithfully reproduced. This means that a large number of bits are required in constructing a character pattern; and, also, that a large capacity memory is needed to store the character patterns. If the bit number of the character pattern and hence the dot density, is reduced, the reliable reproduction of image information is precluded.